#!/usr/bin/node

const Readable = require('stream').Readable;

let rs = new Readable(),
    c  = 'a'.charCodeAt(0);//转成ASCII码

rs.read = () => {
  rs.push(String.fromCharCode(c++));
  if(c>'z'.charCodeAt){
    rs.push(null);
  }
};



rs.pipe(process.stdout);



